The cereal cyst nematode Heterodera latipons Franklin is widespread in the eastern Mediterranean area and often occurs in mixed populations with H. avenae in cereal cropping systems. Differences between the two species in hatching behaviour and development cycle may be factors responsible for the low level of detection of H. latipons in the region. The aim of this study was to investigate the influence of different temperature regimes, agro-ecosystem, sampling date, cyst age and barley root diffusate on the hatching behaviour of H. latipons and its life cycle. The investigations were conducted by observing hatch and development under both field and glasshouse conditions. The optimum temperature for hatching was 10 • C. The hatched second-stage juveniles of H. latipons from the dry and wet agro-ecological zones are found in the soil from December to April with peak densities in January and February. Thirty to 45% of the eggs of both populations from the dry and wet zone hatch slowly over the growing season. The results of hatching tests, simulating pre-planting soil temperatures in Syria, indicate that treatment for 16 days at 5 • C initiates the hatching cycle of H. latipons. There was no significant difference in total hatch when cysts were placed in tap water or in barley root diffusates.